Piping element and manufacturing method and apparatus

ABSTRACT

A piping element having at least two longitudinal components, such as flow pipes ( 4 ), outside of which there is an insulator ( 3 ), outside of which there is a corrugated outer sheath ( 2 ). The piping element is bendable. Fastening means are arranged to the longitudinal components to prevent the longitudinal movement of the longitudinal components in relation to each other.

FIELD OF THE INVENTION

The invention relates to a piping element having at least twolongitudinal components, outside of which there is in an insulator,outside of which there is a corrugated outer sheath, whereby the pipingelement is bendable.

Further, the invention relates to a method for manufacturing a pipingelement, in which method at least two longitudinal components are fed,an insulator is arranged outside the longitudinal components and acorrugated outer sheath is formed outside the insulator.

The invention also relates to an apparatus for manufacturing a pipingelement, the apparatus comprising means for feeding at least twolongitudinal components, means for arranging an insulator outside thelongitudinal components, and an extruder and a corrugator for forming acorrugated outer sheath outside the insulator.

BACKGROUND OF THE INVENTION

U.S. Pat. No. 4,929,409 discloses an apparatus for manufacturing apiping element. Innermost in the piping element, there is a flow pipeand around it an insulator. Outside the insulator, there is a corrugatedouter sheath. The solution of the U.S. patent can be applied to themanufacture of piping elements that have two or more flow pipes. Theflow pipes are then placed in a longitudinal insulation profile havinggrooves or slots for the pipes. The produced piping element is very goodin ring stiffness and is, therefore, especially well suited for use inunderground installations, such as district heating networks. The pipingelement is also flexible and can be coiled for storage and transport.During installation, the piping element is unwound from the coil. Theflow pipes then endeavour to move in the longitudinal direction.Coupling the pipes is, therefore, quite difficult and some extra workingreserve need to be left at the end of the piping element for safety'ssake.

In district heating use, piping elements are also known, in whichpolyurethane foam is sprayed outside the flow pipes, and an outer sheathis arranged outside the polyurethane foam. Because of the polyurethanefoam, this type of piping element is rigid and unbending and itstransport, installation and handling is quite arduous and difficult. Inaddition, when coupling the piping element, the polyurethane foamoutside the flow pipe needs to be stripped away, which is quite arduousand difficult. When the polyurethane foam is stripped, a possible oxygendiffusion protection layer arranged outside the pipe is quite easilydetached, which weakens the working characteristics of the pipingelement considerably.

BRIEF DESCRIPTION OF THE INVENTION

It is an object of the present invention to provide a piping elementthat is improved with respect to the prior art, and a method andapparatus for manufacturing it.

The piping element of the invention is characterized in that the pipingelement comprises fastening means for preventing the longitudinalmovement of the longitudinal components with respect to each other.

Further, the method of the invention is characterized by arrangingfastening means to the longitudinal components to prevent thelongitudinal movement of the longitudinal components with respect toeach other.

Yet further, the apparatus of the invention is characterized in that theapparatus comprises means for arranging fastening means to thelongitudinal components in such a manner that they prevent thelongitudinal movement of the longitudinal components with respect toeach other.

The essential idea of the invention is that the piping element alwayshas at least two longitudinal components, such as flow pipes, andfastening means for preventing the longitudinal movement of thelongitudinal components with respect to each other. Outside thelongitudinal components, there is an insulator and outside theinsulator, there is a corrugated outer sheath, whereby the pipingelement is bendable. The idea of another embodiment is that eachlongitudinal component touches at least one other longitudinalcomponent. The idea of yet another embodiment is that the fasteningmeans are made up of plastic film that is wound in the form of a helicalcurve around the longitudinal components in such a manner that theplastic film touches each longitudinal component.

The invention provides the advantage that the provided piping elementcan be wound into a coil for transport and storage, for instance, andwhen installed from the coil to the usage site, the longitudinalcomponents of the piping element cannot substantially movelongitudinally with respect to each other, whereby the handling andinstallation of the piping element is simple and easy. By arranging eachlongitudinal component to touch at least one other longitudinalcomponent, the piping element becomes compact in cross-section. Theouter diameter of the piping element, for instance, can then be madereasonably small in comparison with a piping element, for instance, inwhich the longitudinal components are placed in the grooves of alongitudinal profile made of insulating material, in which case there isinsulating material between the longitudinal components. As the outerdiameter of the piping element decreases, so does heat loss from thepiping element, because the heat-evaporating sheath is smaller.Similarly, a decrease in the diameter of the piping element providesmaterial savings. Using plastic film, the longitudinal components can befixed in place in a simple, inexpensive and convenient manner.

BRIEF DESCRIPTION OF THE FIGURES

The invention is described in greater detail in the attached drawing, inwhich

FIG. 1 is a schematic partly cross-sectional side view of an apparatusfor manufacturing a piping element, and

FIG. 2 is a schematic cross-sectional side view of a piping element.

In the figures, the invention is shown in a simplified manner for thesake of clarity.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows an apparatus for manufacturing a piping element 1. Thepiping element 1 has a corrugated outer sheath 2. Inside the outersheath 2, there is an insulator 3. Inside the insulator 3, there arelongitudinal components. In the case of FIG. 1, the longitudinalcomponents are flow pipes 4. In addition to or instead of the flow pipes4, the longitudinal components can for instance be cables or protectivepipes or protective profiles for cables installed inside them.

The flow pipes 4 are manufactured in advance and wound into coils 5. Theapparatus thus comprises means for feeding the flow pipes 4 from thecoils 5, but the means that support the coils 5 and enable the feedingof the pipes 4 are not shown in the attached figure for the sake ofclarity. The flow pipes 4 are fed through a winding device 6, in whichplastic film 7 is wound around the pipes 4. Because the flow pipes 4move continuously forward in the apparatus, i.e. to the left in FIG. 1,and the winding device 6 winds the plastic film roll around the pipes 4,the plastic film 7 settles around the pipes 4 in the form of a helicalcurve or spiral. The plastic film 7 is wound tightly around the flowpipes 4 and it touches each of the pipes 4. The plastic film 7 woundaround the flow pipes 4 substantially prevents the longitudinal movementof the pipes 4 with respect to each other when the piping element ishandled, for instance when the piping element 1 is coiled or uncoiled orduring the final installation of the piping element 1 when it is bentand straightened.

The insulator 3 is a prefabricated insulator and it is in a sheet-likeform on a coil 8. For the sake of clarity, FIG. 1 does not show meansfor supporting and turning the coil 8. From the coil 8, the sheet-likeinsulator 3 is fed through a wrapping device 9, in which the sheet-likeinsulator 3 is wrapped around the flow pipes 4. The sides of thesheet-like insulator 3 are joined with a welding device 10. The seamformed by the two sides of the sheet-like insulator 3 placed againsteach other is for instance melted closed with hot air in such a mannerthat the insulator 3 completely surrounds the flow pipes 4. The weldingdevice 10 can also melt the seam closed in some other manner known perse than by utilizing hot air. Instead of the welding device 10, thesides of the sheet-like insulator can also be joined with a gluingdevice, for instance.

The flow pipes 4 and the insulator 3 wrapped around them are led throughthe die 12 of an extruder 11. The extruder 11 and die 12 extrude outsidethe insulator 3 a plastic layer, from which the corrugated outer sheath2 is formed for the piping element 1 in the corrugator 13. Thecorrugator 13 has two sets of moving chill moulds 14 in a manner knownper se. The structure and operation of the extruder 11, die 12 andcorrugator 13 are not described in more detail herein, because they arefully known to a person skilled in the art.

The piping element 1 shown in FIG. 2 has four flow pipes 4. In such acase, two of the pipes are typically made of cross-linked polyethylenePEX equipped with an external oxygen diffusion protection layer and twoare made of conventional unprotected cross-linked polyethylene PEX. Theoxygen diffusion protected pipes 4 are then used for heat piping and theunprotected pipes 4 typically for water supply systems, such as tapwater systems.

The flow pipes 4 are arranged in such a manner that each flow pipe 4touches at least one other flow pipe 4. The plastic film 7 is wound inthe form of a helical curve around the flow pipes 4 so that the plasticfilm 7 touches each of the flow pipes 4 and thus prevents the flow pipes4 from moving longitudinally with respect to each other. The material ofthe plastic film 7 can be low-density polyethylene PE-LD, for instance,and its thickness 20 μm, for instance. The width of the plastic film 7can then be 60 to 120 mm, for instance. The piping element 1 of FIG. 2is compact in structure. When the flow pipes 4 are tightly against eachother, the total diameter of the piping element 1 also becomes quitesmall. Heat loss from the piping element 1 is quite low, because theevaporating sheath is then also quite small. Earlier, a piping elementwith four flow pipes, for instance, has been made by arranging the flowpipes into a longitudinal profile made of an insulating material, and aninsulator and outer sheath has been arranged outside the profile. Theflow pipes 4 then have insulating material between them. When comparingthe piping element of FIG. 2 with the earlier product, it has been notedthat in the earlier solution, in which three of the flow pipes have anouter diameter of 32 mm and one of 18 mm, the outer diameter of thepiping element 1 has had to be 175 mm. In the solution of FIG. 2, ifthree of the flow pipes have an outer diameter of 32 mm and one of 18mm, the outer diameter can be 140 mm. Calculations have proven that thisproduces an 18% saving in material costs and a 16% saving in totalcosts.

The flow pipes 4 are wound in the form of a spiral or a helical curve.This winding also in turn helps in that, when the piping element 1 isbent, the flow pipes 4 do not endeavour to move in relation to eachother. When manufacturing the piping element 1, the flow pipes 4 can bewound with a separate winding device. Conducted tests show, however,that the flow pipes 4 try to some extent to wind in relation to eachother even without any separate winding arrangement. It has been foundthat this type of self-winding provides a suitable winding in mostcases.

The insulator 3 is most preferably made of cross-linked closed-cellpolyethylene foam. The insulator 3 can be formed of severalprefabricated insulating sheet layers. The thicknesses of the differentlayers can be the same. Naturally, the width of an outer layer must begreater than that of an inner layer.

The corrugated outer sheath 2 is most preferably made of polyethylenePE. Most preferably, the longitudinal components, such as the flow pipes4, insulator 3 and outer sheath 2, of the piping element 1 are all madeof either cross-linked or conventional polyethylene. For instance, thehandling of the piping element 1 during winding is then simple and easy.It is naturally also possible to use other materials. For instance, theinsulator 3 can also be made of foamed polypropylene. Correspondingly,the outer sheath 2 can also be made of polypropylene.

The fact that the outer sheath 2 is corrugated makes the ring stiffnessof the piping element 1 quite good, for instance 8 to 12 kN/m². Thepiping element 1 is especially well suited for underground use. Possibleapplications are district heating networks and tap water systems, forinstance. Due to the corrugation and the softness of the insulator 3,the piping element is bendable. The fact that the piping element 1 isbendable means that the piping element can be coiled for storage andtransport and uncoiled for installation. The outer diameter of thepiping element 1 can typically be 100 to 300 mm. Piping elements 1 ofthis kind can be coiled for storage and transport into a coil with adiameter of 0.8 to 3 m, for instance.

The drawing and the related description are intended only to illustratethe idea of the invention. The invention may vary in detail within thescope of the claims. Thus, most preferably, the insulating layer isformed of a prefabricated insulating sheet. The insulator can, however,also be made of a material that is prefabricated into a tube, in whichcase the tube has a longitudinal slot, through which the longitudinalcomponents, such as flow pipes 4, are installed inside the insulatingtube. When the longitudinal component is a protective pipe or profile,inside which a cable is to be installed, the binding of the longitudinalcomponents makes it possible to pass the cable into the protective pipeor profile in such a manner that the protective profile or pipe does notessentially move longitudinally. The cable can for instance be a heatingcable for heating the flow pipe 4 and the fluid in it, or some othercable can be passed into the protective profile or pipe that is in noway related to the main purpose of use of the piping element.

Further, the longitudinal component can also be a longitudinalintermediate insulation profile that is placed between the flow pipes.The cross-section of the longitudinal intermediate insulation profilecan have many shapes. At its simplest, the longitudinal intermediateinsulation profile can be a longitudinal intermediate insulation sheet.The longitudinal intermediate insulation sheet can be rectangular incross-section or it can have one or more grooves and/or protrusions. Thepiping element 1 can for instance have four flow pipes 4, in which casethe longitudinal intermediate insulation sheet is arranged between theflow pipes 4 in such a manner that it has two flow pipes 4 on each side.In such a solution, the piping element 1 can have the pipes of a hotwater system on one side and the pipes of a tap water system on theother side of the intermediate insulation sheet. The longitudinalintermediate insulation sheet then prevents heat transmission betweenthe flow pipes 4 of the different systems. A longitudinal intermediateinsulation profile can be made of closed-cell polyethylene foam, forinstance. In this embodiment, too, fastening means preferably preventthe longitudinal movement of all longitudinal components with respect toeach other.

1. A piping element having at least two longitudinal components, outsideof which there is an insulator, outside of which there is a corrugatedouter sheath, whereby the piping element is bendable, wherein the pipingelement comprises fastening means for preventing the longitudinalmovement of the longitudinal components with respect to each other.
 2. Apiping element as claimed in claim 1, wherein the fastening means aremade up of plastic film that is wound outside the longitudinalcomponents in the form of helical curve and arranged to touch each ofthe longitudinal components.
 3. A piping element as claimed in claim 1,wherein each of the longitudinal components touches at least one otherlongitudinal component.
 4. A piping element as claimed in claim 1,wherein at least two of the longitudinal components are flow pipes.
 5. Apiping element as claimed in claim 4, wherein at least one of thelongitudinal components is a longitudinal intermediate insulationprofile, which is arranged between the flow pipes with at least one flowpipe on each side.
 6. A piping element as claimed in claim 4, whereinfour of the longitudinal components are flow pipes and one alongitudinal intermediate insulation sheet, and the longitudinalintermediate insulation sheet is arranged between the flow pipes withtwo flow pipes on each side.
 7. A piping element as claimed in claim 1,wherein the insulator is made of a material prefabricated before thepiping element is made.
 8. A piping element as claimed in claim 7,wherein the insulator is made of an insulation sheet wrapped around thelongitudinal components.
 9. A piping element as claimed in claim 1,wherein the insulator is made of an elastic material.
 10. A pipingelement as claimed in claim 9, wherein the insulator is made ofcross-linked closed-cell polyethylene foam.
 11. A piping element asclaimed in claim 1, wherein the piping element is arranged to beinstalled underground.
 12. A method for manufacturing a piping element,in which method at least two longitudinal components are fed, aninsulator is arranged outside the longitudinal components, and acorrugated outer sheath is formed outside the insulator characterized byarranging fastening means to the longitudinal components to prevent thelongitudinal movement of the longitudinal components with respect toeach other.
 13. A method as claimed in claim 12, characterized bywinding plastic film outside the longitudinal components in the form ofa helical curve and arranging the plastic film to touch each of thelongitudinal components.
 14. A method as claimed in claim, characterizedby forming the insulator by wrapping an insulation sheet around thelongitudinal components
 15. An apparatus for manufacturing a pipingelement, the apparatus comprising means for feeding at least twolongitudinal components, means for arranging an insulator outside thelongitudinal components, and an extruder and a corrugator for forming acorrugated outer sheath outside the insulator, wherein the apparatuscomprises means for arranging fastening means to the longitudinalcomponents in such a manner that the fastening means prevent thelongitudinal movement of the longitudinal components with respect toeach other.
 16. An apparatus as claimed in claim 15, wherein theapparatus comprises a winding device for winding plastic film in theform of a helical curve around the longitudinal components to touch eachof the longitudinal components.
 17. An apparatus as claimed in claim 15,wherein the apparatus comprises means for arranging a prefabricatedinsulator around the longitudinal components.
 18. An apparatus asclaimed in claim 17, wherein the apparatus comprises a wrapping devicefor wrapping a prefabricated insulation sheet around the longitudinalcomponents.
 19. A piping element as claimed in claim 2, wherein each ofthe longitudinal components touches at least one other longitudinalcomponent.
 20. A piping element as claimed in claim 2, wherein at leasttwo of the longitudinal components are flow pipes.